Four Berry Jam - cooking recipe

Ingredients

1 cup fresh blackberries (or frozen unsweetened, thawed and undrained)
1 cup fresh blueberries (or frozen unsweetened, thawed and undrained)
1 1/2 cups fresh strawberries (or frozen unsweetened, thawed and undrained)
1 1/2 cups fresh raspberries (or frozen unsweetened, thawed and undrained)
1 (1 3/4 ounce) box pectin (not low-sugar or no-sugar varieties)
7 cups sugar

Preparation

Prepare your jars in advance--sterilize them and keep the jars, lids, and rings warm while preparing the jam. Have all tools ready and handy (ladle, towel, wet cloth, canning jar funnel, etc).
Crush berries in a large, non-reactive (such as stainless steel) saucepot. Stir in pectin until dissolved.
Bring to a full, rolling boil over high heat, stirring constantly to avoid scorching (reduce heat to medium-high if needed).
Stir in sugar. Return to a full, rolling boil and boil for exactly 1 minute (starting from when you can no longer stir the bubbles down).
Remove from heat and quickly skim off any foam. You must move quickly at this point to prevent the jam from cooling off too much.
Quickly ladle hot jam into hot, sterilized jars, leaving 1/4 inch headspace.
Wipe rims with a clean, warm, damp cloth to ensure a good seal. Place lids on jars and screw rings on snugly but not too tight. Flip jars upside down. Let stand upside down for 5 minutes, then turn right-side up again. Let sit for one hour.
After one hour, check seals. If any lids are still popped up (there is a bump in the center of the lid that should be down if the jar is sealed, and up if not), then refrigerate and use immediately, or process in a hot water bath for 10 minutes.
Store jars in a cool, dark place until ready to use; use within 1 year.